The process cartridge can be detachably mounted into a main part of an image forming apparatus, and the process cartridge, as a whole unit, comprises of an electrophotographic photosensitive member and at least one of processing means such as charging means, developing means, cleaning means, or the like. Since the process cartridge is detachably mountable relative to the main part of the device, it is easy to maintain the device. An electrophotographic image forming apparatus functions through electrophotographic image formation in the manner that an electrostatic latent image is formed by selectively exposing the electrophotographic photosensitive member uniformly charged by a charger to light from the image forming apparatus. The electrostatic latent image is developed with toner by a developing means into a toner image. The toner image thus formed is transferred onto a recording medium by a transferring means to form an image on the recording material.
As shown in FIG. 1, the prior art has disclosed a method of transmitting the driving force between a photosensitive drum driving head 17 provided to the process cartridge and a image forming apparatus driving head 18, wherein a spiral triangular recess 18a is provided at an end of the image forming apparatus driving head 18, and a spiral triangular projection 17a is provided correspondingly at an end of the photosensitive drum driving head 17 in complementary with the triangular recess 18a for transmission. This method is effective for transmitting the driving force. However, the process of manufacturing such a spiral triangular projection 17a is complicated, the cost of making mould is high, and the photosensitive drum driving head 17 is easy to deform or damage during long time operation, which will affect the driving accuracy and efficiency.
Additionally, according to the prior art, manufacturing spiral projection and spiral recess requires high accuracy, so there is frequently poor contact between the spiral triangular projection 17a and triangular recess 18a. It is difficult for the rotating center of the triangular recess 18a to achieve coaxial centering, which causes unnecessary sloshing between the projection and the recess during driving force transmission.
Thus, in configuration and use, conventional process cartridges still has disadvantages and defects to be further improved. To solve the problems, every concerned manufacturer brainstorms for a better solution. However, since years ago, no suitable device has been developed and any existing product lacks of appropriate structure for the improvement as well. Obviously, person skilled in the art may be anxious to approach to the problems. Therefore, how to invent a process cartridge with new structure is indeed one of the most important studies recently, also an object in the current industry.
In view of said defects of the process cartridges in existence, the present inventor, based on his practical experience and specialized knowledge in the design and manufacture of such products for many years, is working on research and innovation in combination of theory for designing a process cartridge with non-conventional structure so as to improve the prior technology and make it more commercial. Through continual invention and modification, together with repetitiously preparing samples and making improvements, the present invention having certain practical value is finally created.